The invention relates to a doctor blade for a fiber web machine, the doctor blade including a blade section and a fastening detent section. The invention also relates to a doctor arrangement in a fiber web machine.
Various doctor blades are used in a fiber web machine mainly for keeping the roll surfaces clean. Doctor blades can also be used for dewatering, for example, at a suction roll. Conventionally, the blade section is composed of a plate-like component having one of its edges chamfered and the edge opposite to the chamfer arranged as a fastening detent. Rivets are used in thin doctor blades, and particularly in thick doctor blades, the fastening detent can be formed in the basic material of the doctor blade. The fastening detent section ensures that the doctor blade keeps in place in the blade holder. Doctor blades are usually made of metal, plastic, fiber-reinforced plastic, or a plastic composition. Some known doctor blades are proposed in Finnish patent app. No. 20065601.
However, known doctor blades have a number of shortcomings. Firstly, several positions require a certain kind of doctor blade, which increases the number of different doctor blades in a fiber web machine. Moreover, blade holders may set additional requirements for doctor blades. For doctoring of particularly soft-surfaced rolls or belts, plastic blades are used which bend disadvantageously and the blade section of which becomes easily swaged. Plastic blades also bend easily during storage. Adaptation of a bent doctor blade to the roll surface is incomplete, which causes, for example, unevenness in the contact profile or an otherwise incomplete doctoring result. Disturbances in doctoring cause web breaks and local surface pressure variations shorten the fabric life.